The present invention is directed to water heaters and similar systems in which a liquid reservoir is interposed in a pressurized line.
Most water heaters include a pressure vessel that admits water supplied under pressure and, after heating, supplies the heated water under pressure to faucets and other terminal devices in the house that the water heater serves. Although water heaters do generally provide a reasonably long useful life, all eventually fail, and some common failure modes involve a rupture or leak of the pressure vessel. Such a failure can result in the release of a large amount of water; the water release can continue indefinitely if it is not detected, and in some cases the resultant economic loss is considerable.
It would therefore seem desirable to provide water heaters with automatically operated shut-off valves that stop the flow of water into the vessel when a leak occurs. Few such water heaters exist, however, because it is not ordinarily convenient to detect a leak by monitoring readily sensed physical quantities. For example, water pressure would not be a good leak indicator, because the pressure reduction, if any, caused by a leak would not be any greater than that which results from ordinary hot-water use unless the leak resulted from an atypically severe rupture. To sense a leak would therefore require a more-elaborate sensing scheme, such as a sensor for monitoring for moisture on the floor near the water heater. Clearly, such an approach would only rarely be practical.